Rickrickboom

So I have this issue and hope that someone can help me because it is starting to drive me crazy. I recently purchased a 2004 ZD30di GU patrol and it has been an absolute beauty. But unfortunately something has started that has been getting on my nerves. Over the past couple weeks it has developed this incessant squeaking coming from the pulleys, which is very embarrassing and not very nice to listen to. Now the seller has been very helpful, going as far as providing me a new tensioner and even fitting it on one occasion. I was very adament that it was tensioner pulley and that it would be the end of it. But it wasn't to be so. The squeaking has become a little worse over the past couple days, and to make matters worse, I tried spraying the pulleys with WD40, noticing that the squeaking only stopped when I sprayed the crank pulley. Now this worries me a lot. I have not read anywhere that the crank pulley will make this sound at any time, and knowing the cost to have a crank pulley done I am really starting to have my doubts that this is going to be a cheap or quick fix. My question is this: has anyone had this sort of problem at all and what did it end up being that was your fix? Is there a possibility that it is the crank pulley at all and what would be my best course of action to rectify this problem. Thanks in advance Mick